Durango Nature Studies

The Subnivean World is Vital to Ecosystem Health

One of my favorite things about work is the office banter that occurs when our educators plan lessons for our education and after-school programs. Last week, the education team was discussing the next series of lessons for Nature Club, our after-school enrichment program that takes place at five of Durango 9R’s elementary schools. We Durangoans all seem to be reveling in our snowy year, so it may come as no surprise that the discussion on next lessons focused on snow — specifically introducing Nature Club participants to the wonders of the subnivean world — the world beneath the snow.

For most of us, a snowy landscape may depict serenity and quiet. For many others, it beckons us to the backcountry for adventure and excitement. Rarely do we think about what happens under the snow, but that’s where some truly fascinating activity happens. The subnivean zone plays an important role in the life cycle of both plants and animals.

Beneath the snow, rodents and other small mammals spend most of the winter scurrying around in subnivean tunnels where temperatures remain consistently around 32 degrees. Small mammals living in this zone can endure harsh winter conditions. When their populations thrive, they provide a valuable food source for other animals who prey upon them throughout the winter, enhancing these predators’ ability to endure winters as well.

Not only is the subnivean zone important in animals’ lives, but it also has a critical role when it comes to plants and carbon and nitrogen cycles. When temperatures drop below freezing, ice crystals cause plant cells to rupture, releasing carbon dioxide that the plant stored during the summer growing season. Research indicates that a plant may release up to half of its stored carbon upon freezing.

The timing of snow’s arrival each winter can make a significant difference in the health of an ecosystem and not only for the importance to our watersheds. If snow falls soon after the first freeze, the subnivean zone insulates the plant, and release of carbon from the plant will slow. Additionally, the thawing will initiate a break down of the plant, and it will serve as food for microbes and other scavengers. Subnivean microbes absorb nitrogen from the snow and decomposing plants and store it. When spring comes, the nitrogen is released into the soil about the time plants start growing again, providing a readily-available source of nutrients. This dance between plants, animals, and microbes throughout a season we consider dormant is truly amazing. It is a delicate balance that can easily be disrupted by changing weather patterns.